Soil quality and productivity usually decline with long-term monoculture of Cunninghamia lanceolata. To clarify the soil improvement potential of native broad-leaved tree species in subtropical regions on degraded C. lanceolata plantation, we focused on three kinds of broad-leaved monoculture of Phoebe bournei, Schima superba, and Cyclobalanopsis gilva, using C. lanceolata harvested plantation as control. We examined the responses of soil physicochemical properties in different soil layers (0-20, 20-40, and 40-60 cm) after transforming a pure Chinese fir forest into pure broad-leaved forests. The results showed that broad-leaved pure plantations improved the quality of surface soil (0-20 cm), with P. bournei pure plantation showing the greatest improvement in soil pore structure and water retention. Compared with the C. lanceolata pure plantation, soil total porosity, capillary porosity, capi-llary water-holding capacity and field water-holding capacity in the surface layer of P. bournei pure plantation increased by 6.4%-11.7%, while the mass water content was significantly increased by 28.7%. S. superba pure plantation showed obvious advantages in enhancing soil organic carbon and total nitrogen content, which were 2.8 and 3.6 times that of the C. lanceolata pure plantation, and 2.5 and 2.0 times that of the control, respectively. C. gilva pure plantation performed better in promoting available nutrients accumulation. The contents of alkali-hydrolyzable nitrogen and available phosphorus in the surface layer increased by 89.8% and 204.9% respectively compared with the C. lanceolata monoculture, and increased by 36.4% and 85.8% respectively compared with the control. With the deepening of soil layer, the improvement advantages of broad-leaved pure plantations significantly diminished. In the 40-60 cm soil layer of three broad-leaved pure plantation, soil bulk density increased by 8.7%-11.4% compared with the surface layer, while porosity, water-holding capacity, and the contents of soil organic carbon, total nitrogen, available nitrogen, and available phosphorus decreased by 15.4%-52.4% compared with the surface layer. The content of total phosphorus, available phosphorus, and available potassium in the 40-60 cm soil layer were generally low, indicating that there were still phosphorus and potassium limitations in the deep soil after the broad-leaved transformation of degraded C. lanceolata plantation. Correlation analysis showed that the maxi-mum water-holding capacity, capillary water-holding capacity and field water-holding capacity were significantly positively correlated with total porosity and capillary porosity, but significantly negatively correlated with soil bulk density. Soil organic carbon content was significantly positively correlated with total nitrogen, alkaline hydrolysable nitrogen, and available phosphorus, indicating that soil pore structure determined water holding capacity, while organic matter accumulation contributed to the enhancement of nutrient availability. Therefore, converting degraded C. lanceolata plantation into broad-leaved pure plantation of S. superba, P. bournei, and C. gilva, could significantly improve soil quality of surface layer, but the effect on deep soil remained limited.

We focused on soils from coniferous-broadleaf mixed forests in the transition zone between warm tempe-rate and subtropical climates. Based on a 9-year field manipulative experiment with factorial treatments of nitrogen addition (50 kg N·hm^-2·a^-1) and drought (50% precipitation reduction). Soil extracellular enzyme activities involved in carbon, nitrogen, and phosphorus cycling and their stoichiometric characteristics were determined. Results showed that nitrogen addition significantly increased the activity of soil β-glucosidase (βG), soil enzyme stoichiometric carbon-nitrogen ratio (E_C:N) and soil enzyme stoichiometric carbon-phosphorus ratio (E_C:P) by 113.1%, 158.5%, and 126.8%, respectively. Drought significantly reduced the activity of soil acid phosphatase (AP) by 69.3%, while E_C:N and E_C:P increased significantly by 125.9% and 133.0%. Nitrogen addition combined with drought treatment significantly increased soil βG activity and E_C:P by 106.5% and 129.8%, respectively. Additionally, nitrogen addition combined with drought treatment significantly increased soil AP and β-N-acetylglucosaminidase (NAG) activities, whereas drought attenuated the positive effects of nitrogen addition on soil βG, E_C:N, and E_C:P. Soil cellulose hydrolase (CBH) activity was significantly positively correlated with soil water content. Soil βG activity was significantly positively correlated with dissolved organic carbon, nitrate, and ammonium. Soil AP activity was significantly positively correlated with ammonium. Soil NAG activity was significantly positively correlated with dissolved organic carbon and ammonium. In conclusion, nitrogen addition and drought interactively affected soil extracellular enzyme activities and their stoichiometric characteristics in a warm-temperate to subtropical mixed coniferous and broad-leaved forest, indicating that drought may alter the influence of nitrogen addition on soil microbial enzymatic strategies for nutrient acquisition.

To investigate the responses of soil microbe-mediated carbon (C), nitrogen (N), and phosphorus (P) across different regeneration forests following severe fire disturbance in cold-temperate region, and to clarify the characteristics of microbial nutrient cycling and resource limitation in post fire soils, we selected five typical forest types (34 years post the Black Dragon Fire in the northern Greater Khingan Mountains): Larix gmelinii plantation, L. gmelinii and Betula platyphylla mixed plantation, Pinus sylvestris var. mongolica plantation, P. sylvestris var. mongolica and B. platyphylla mixed plantation, naturally regenerated forest of L. gmelinii. We measured soil microbial biomass C (MBC), N (MBN), and P (MBP) contents, and analyzed their stoichiometric ratios, microbial quotients, and soil-microbe stoichiometric imbalances. The results showed that there were significant differences in soil microbial biomass and stoichiometric ratios among the five forest types. Naturally regenerated forest of L. gmelinii had the lowest soil MBC (455.79 mg·kg^-1) and MBN (25.93 mg·kg^-1) contents, while the P. sylvestris var. mongolica plantation had the lowest soil MBP content (9.81 mg·kg^-1). The naturally regenerated forest of L. gmelinii exhibited the highest MBC:MBN (17.77) and the lowest MBC:MBP (28.11) and MBN:MBP (1.59). Across all postfire regeneration stands, soil MBC:MBN ranged from 10 to 18, indicating fungi dominated soil microbial community. The MBN:MBP was consistently below 6.9, suggesting that soil metabolism was likely limited by nitrogen. The soil microbial quotients in the monocultures and mixed plantations were generally higher than those in the naturally regenerated forest. The soil microbial quotient of C was significantly higher in P. sylvestris var. mongolica plantation (monoculture: 2.0%; mixed plantation: 2.3%) than in L. gmelinii stands (monoculture: 1.4%; mixed plantation: 1.1%). The soil-microbe C:N stoichiometric imbalance was greatest in the L. gmelinii plantation (1.87) and smallest in the P. sylvestris var. mongolica and B. platyphylla mixed plantation (0.77). Both C:P and N:P stoichiometric imbalance were the lowest in the P. sylvestris var. mongolica plantation (0.80 and 0.72, respectively). For post fire forest management in the Greater Khingan Mountains, we recommended monoculture and mixed plantation regeneration to increase soil microbial biomass and enhance C-N-P turnover potential. Regarding tree species, regenerated forests dominated by P. sylvestris var. mongolica were beneficial to overall soil resources.

We investigated the differences in ecological stoichiometric characteristics between aboveground and belowground components across five typical vegetation types in the Luo Mountain, Ningxia, including desert steppe, shallow mountain shrubland, broadleaf forest, mixed coniferous and broad-leaved forest, and coniferous forest. We examined the allometric growth relationships and homeostasis features of aboveground and belowground stoichiome-try, and analyze the main litter and soil nutrients influencing ecological stoichiometry. Results showed that leaf carbon (C), nitrogen (N), and phosphorus (P) contents were significantly higher than roots across all vegetation types. Desert steppe exhibited the highest leaf C content (464.45 g·kg^-1), being significantly higher than the three forest types, while its root C content was the lowest (235.44 g·kg^-1). Shallow mountain shrubland had the lowest leaf N and P contents (18.43 and 0.58 g·kg^-1, respectively), while its leaf C/N, C/P, and N/P were the highest (24.9, 795.5, and 31.9, respectively). The five vegetation types exhibited significant negative allometric relationship between leaf and root C contents. There was significant positive allometric relationship for leaf and root P contents. Leaf C-P exhibited negative allometry, whereas leaf N-P and root C-N showed isometric growth. Leaf and root N contents, along with C/N, C/P, and N/P, remained absolutely stable, while P content was consistently sensitive. Litter N/P had the greatest impact on leaf stoichiometry, while litter C/P most influenced root stoichio-metry. Aboveground nutrient allocation was higher than belowground part in all vegetation types of Luo Mountain, with shallow mountain shrubland adopting a more conservative resource utilization strategy, while the other vegetation types tended to be resource acquisition. There was a trade-off for C allocation in Luo Mountain plants, but a synergistic strategy for P allocation.

We investigated pure Eucalyptus urophylla × E. grandis plantations (PP) and their mixtures with Erythrophleum fordii (EE), Dalbergia odorifera (ED), Castanopsis hystrix (EC), and Parashorea chinensis (EP), and studied soil phosphorus (P) fractions, soil physicochemical properties, fine-root traits of the dominant E. urophylla × E. grandis, microbial biomass, and extracellular enzyme activities in the 0-20 cm layer, as well as their interrelationships. We analyzed the mechanisms underlying the effects of mixed plantations of E. urophylla × E. grandis on soil P fractions. The results showed that, compared with PP, EE and EC significantly increased labile P by 77.7% and 28.2%, moderately labile P by 25.4% and 13.4%, respectively. ED significantly increased moderately labile P by 24.2%, whereas EP significantly increased labile P by 44.3%. Furthermore, compared with PP, EE and EC had significantly higher soil organic carbon, microbial biomass carbon, and activities of C- and N-acquiring enzymes. ED significantly increased soil ammonium and nitrate, accompanied by a significant decline in C- and N-acquiring enzyme activities. EP exhibited significant reductions in both soil total nitrogen and the activities of C- and N-acquiring enzymes. Mixed plantations increased acid phosphatase activity by 24.7%-43.5%. Random forest analysis indicated that soil microbial biomass carbon, fine-root P content and root surface area of the dominant E. urophylla × E. grandis, and N-acetyl-β-glucosaminidase were the primary drivers of labile and moderately labile P. Structural equation modeling indicated that mixed plantations influenced the content and availability of soil P fractions by modulating fine-root traits and soil microbial metabolic traits. Overall, our results indicated that establishing EE and EC mixtures represented particularly effective strategies for improving soil P availability in Eucalyptus plantations.

We analyzed the stoichiometry of carbon, nitrogen, and phosphorus in different organs of Nitraria tangutorum (roots, stems, and leaves) and soil across four succession stages in nebkhas in the desert-oasis ecotone: initial, developing, stable, and declining. The results showed that soil organic carbon, total nitrogen, total phosphorus, C:N, and C:P all peaked at the stable stage and then decreased, with reductions ranging from 25.9% to 64.9%, while the N:P was highest at the declining stage, increasing by 42.8% relative to the initial stage. Across all stages, leaf N and P contents were significantly higher than those in stems and roots. As succession progressed, stem and root C contents first increased and then decreased, peaking at the developing stage, with respective increases of 13.3% and 27.7%. Leaf and stem N contents were highest at the stable stage, with increases of 26.0% and 12.3%, respectively. Root N content declined by 40.7%. Stem and root P contents were lowest at the stable stage but rebounded significantly at the declining stage, increasing by 34.2% and 34.5%, respectively. The C:N and C:P of roots and stems initially increased and then decreased, peaking at either the developing or stable stages. In contrast, leaf C:N showed a gradual decline, leaf C:P first decreased and then increased, and leaf N:P gradually increased with succession. Multivariate analyses indicated that nebkha succession positively regulated soil physi-cochemical properties and root stoichiometric characteristics, while indirectly negatively regulating those of stems and leaves, thereby driving the plant-soil system away from nutrient accumulation toward depletion, and shifting nutrient limitation status from N limitation to N and P co-limitation.

Based on a 9-year nitrogen (N) addition experiment in a subtropical evergreen broad-leaved forest at the Fujian Sanming Forest Ecosystem National Field Observation and Research Station, we examined the effects of long-term N addition on soil microbial respiration and metabolic quotient (qCO₂). We collected surface soils (0-10 cm) from control (CK, 0 kg N·hm^-2·a^-1), low nitrogen (LN, 40 kg N·hm^-2·a^-1), and high nitrogen (HN, 80 kg N·hm^-2·a^-1) treatments, analyzed soil physicochemical properties, microbial biomass, and the stoichiometric characteristics of extracellular enzymes related to carbon (C), N, and phosphorus (P), and measured the soil microbial respiration through laboratory incubation experiments. The results showed that the HN treatment significantly decreased the soil C/N by 18.8% and increased the soil N/P by 52.9%. The LN and HN treatments significantly decreased the dissolved organic C/N by 31.8% and 34.6%, and increased the microbial N/P by 72.8% and 29.8%, respectively. Microbial respiration in the LN treatment was significantly higher than that in the HN treatment, with no differences observed between either treatment and CK. The qCO₂ in the LN and HN treatments was significantly increased by 36.8% and 21.1%, respectively, and the qCO₂ in the LN treatment was significantly higher than that in the HN treatment. Stepwise regression analysis indicated that soil C/N and microbial N/P were the primary factors influencing the microbial respiration and qCO₂, accounting for 56.2% and 58.4% of the variance, respectively. In conclusion, the effects of long-term N deposition on soil microbial respiration and metabolic quotient in subtropical forests were dose-dependent. High N deposition suppressed microbial respiration by reducing soil C/N, whereas low N deposition increased microbial metabolic quotient by exacerbating microbial N/P imbalance.

We employed a common garden experiment to simulate climate warming, based on which we investigated the responses of non-structural carbohydrates (NSC), soluble sugars (SS), starch (ST) concentrations and the SS/ST in fine, medium, and coarse roots of 11 provenances of Larix gmelinii at the end of the growing season. The results showed that climate warming significantly decreased NSC concentration, SS concentration and SS/ST by 8.0%-10.6%, 16.4%-24.5% and 25.3%-30.8%, respectively, across all root types. ST concentration in the fine and middle roots significantly increased by 9.9%-15.3%, and ST concentration in the coarse roots varied insignificantly. As root diameter increased, the decrease in SS concentration showed an increasing trend, while the increase in ST concentration showed a decreasing trend. The warming-induced changes in NSC concentration, SS concentration, and SS/ST across different root diameter classes after climate warming, namely the warming effect, were significantly and positively correlated with aridity index (AI) of the seed collection sites. In contrast, the warming effect on ST was significantly and negatively correlated with AI. L. gmelinii adapted to climate warming by regulating NSC concentration and the proportions of its components in roots of different diameter classes, and this capacity varied among provenances. The effects of root diameter class and provenance should be considered when investigating the responses of root NSC to climate warming.

To reveal root adaptive mechanisms of Pinus koraiensis after being introduced to the Daxing’an Mountains, we used 50-year-old P. koraiensis plantations in the introduction areas (Nanmu and Jiagedaqi) as study objects, with the natural distribution area (Dailing) as the control. We analyzed the regional variation characteristics, resource trade-off strategies, and key environmental driving factors of functional traits of first- to third-order fine roots. The results showed that, compared with the natural distribution area, the third-order root tissue density in the Nanmu decreased significantly by 7.2%, and the specific root area increased significantly by 15.0%. The nitrogen content of first- to third-order roots decreased significantly by 28.6%, 21.3% and 26.4%, respectively. The carbon content of second and third order roots decreased significantly by 4.2% and 4.0%, respectively. The third order root stele diameter decreased significantly by 20.8%; and the cortex thickness of first and third order roots increased significantly by 36.2% and 45.7%, respectively. In the Jiagedaqi, the third-order root diameter and tissue density decreased significantly by 14.8% and 9.0%, respectively; the specific root area increased significantly by 29.4%; the nitrogen content of first- to third-order roots decreased significantly by 32.0%, 27.1% and 28.1%, respectively. The third-order root carbon content decreased significantly by 3.9%. The stele diameter of first- to third-order roots decreased significantly by 30.8%, 33.5% and 22.0%, respectively. The cortex thickness of first and third order roots increased significantly by 39.3% and 27.3%, respectively. There were significant differences between the two introduction areas in certain functional traits. The first- to third-order roots of P. koraiensis exhibited a two-dimensional ecological strategy space, with the resource acquisition-conservation trade-off axis being domi-nant. Roots in the natural distribution area tended toward a resource-conservative strategy, while those in the introduction areas tended toward a resource-acquisitive strategy. The foraging-collaboration axis was secondary, with no difference between the two distribution areas. This differentiation in resource acquisition-conservation trade-off was mainly driven by the dual limitation of soil nutrients and water in the introduction areas, where insufficient resource supply promoted a resource-acquisitive strategy. However, this resource deficiency was mainly manifested in the functional traits of specific root orders rather than the overall root strategy. In conclusion, P. koraiensis could synergistically adjust root functional traits during the introduction process, shifting from a resource-conservative to a resource-acquisitive strategy, thereby adapting to the relatively nutrient- and water-limited environment of the Daxing’an Mountains.

We developed a health assessment system for arboreal species in street green spaces of Xiong’an New Area, which comprised 12 indicators with four dimensions: whole-tree, crown, foliage, and trunk, with health grades classified into levels Ⅰ-Ⅴ (corresponding to healthy, sub-healthy, moderate healthy, unhealthy, and mori-bund, respectively). We surveyed 24 roads with 1040 trees, belonging to 32 species, 17 genera, and 11 families. Healthy and sub-healthy individuals together accounted for 63.8%, while unhealthy and moribund trees accounted for 11.0% and 4.0%, respectively. The three tree species with the highest application frequency were Styphnolo-bium japonicum, Fraxinus chinensis, and Ginkgo biloba. There were significant differences in health status among the 14 tree species with application frequency >5%. Pinus bungeana exhibited the highest health grade, while Acer ×freemanii, G. biloba, Prunus ×yedoensis ‘Somei-yoshino’, and Prunus cerasifera ‘Atropurpurea’ showed relatively lower health grades. Nine factors were significantly correlated with tree health in the street green spaces of Xiong’an New Area, including crown width, tree height, species origin, adjacent land use type, planting scenario, tree pit type, underlying surface composition, planting time, and pruning intensity. Furthermore, there were significant interactive effects with tree species for crown width and pruning intensity. Arboreal trees in the street green spaces of Xiong’an New Area faced certain health risks. Prioritizing stress-resistant native species, improving site conditions according to species-specific requirements, standardizing planting and construction practices, and implementing precise maintenance management were key measures to enhance tree health.

Biological soil crusts (or biocrusts) exert a critical influence on carbon cycling in arid and semi-arid ecosystems. However, the contribution of biocrusts to soil respiration and the mechanisms underlying their environmental responses remain unresolved, hindering accurate quantification of soil carbon efflux in drylands. In this study, we conducted continuous in-situ monitoring of respiration rates, soil temperature, soil moisture, and rainfall of mixed biocrust communities (biocrust-covered soils versus biocrust-removed bare soils) on the Loess Plateau to investigate the contribution of biocrusts to soil respiration and their responses to those three factors. The results showed that the range of soil respiration rates was 0.07 to 1.66 μmol·m^-2·s^-1 in biocrust-covered soils and was -0.09 to 1.59 μmol·m^-2·s^-1 in biocrust-removed bare soils, with the former being significantly greater than the latter. The respiratory effect of the biocrust layer (calculated as the difference in respiration rate between biocrust-covered soils and biocrust-removed bare soils) ranged from -0.33 to 0.93 μmol·m^-2·s^-1, with its relative contribution to total soil respiration varying from -31% to 213%. Rainfall modulated both the respiratory effect of biocrust layer and its contribution to soil respiration. The average contribution of biocrust to soil respiration was -6% under rainfall-free conditions and was 27% during rainfall periods. The relative contribution of the biocrust layer to soil respiration was significantly positively correlated with soil moisture and rainfall amount, but negatively correlated with soil temperature. Rainfall explained the largest proportion of variance in biocrust contribution, indicating that rainfall was the primary driver of biocrust effects on soil respiration on the Loess Plateau. These findings could provide critical baseline data to support accurate assessments of biocrust effects on soil respiration in the context of climate change.

We investigated Artemisia scoparia community across a natural precipitation gradient in the temperate steppe region, including desert (mean annual precipitation was 220.18 mm), desert steppe (287.71 mm), and typical steppe (399.11 mm) habitats, and analyzed interspecific relationships and community stability. The results showed that a total of 15 herbaceous species were recorded across three types of habitats, dominated by species from Poaceae and Asteraceae. A. scoparia had relatively high importance values at all sites, indicating its dominance in the plant communities. However, its importance value in the typical steppe (6.5) was lower than that in areas with less precipitation, being 13.9 in the desert and 21.0 in the desert steppe. The niche overlap among most plant species in the community was low, with the proportion of niche overlap indices (O_ik) <0.5 being 86.7%, 89.3%, and 97.8% in desert, desert steppe, and typical steppe, respectively, indicating significant differentiation of resource utilization among species. The niche breadth of A. scoparia in desert steppe (Levins’s niche breadth index of 7.70 and Shannon’s niche breadth index of 2.22) was higher than that in desert and typical steppe. Plant species in the study area were mainly negatively associated, and the community structure was relatively loose. A. scoparia communities in desert, desert steppe, and typical steppe did not reach a stable state and were in a non-stable dynamic succession stage, with the A. scoparia community in desert steppe exhibiting relatively higher stability.

Based on a long-term nitrogen (N) addition experiment in the Sanjiang Plain wetland, we measured leaf photosynthetic physiology, morphological structure, and ecological stoichiometric characteristics of the dominant species Calamagrostis angustifolia among three treatments: control (0 g N·m^-2·a^-1), low N (4 g N·m^-2·a^-1), and high N (8 g N·m^-2·a^-1). We elucidated the response patterns and adaptive strategies of its functional traits after 14 years chronic N inputs. The results showed that 14 leaf functional traits responded differently to long-term N addition. Under the low N treatment, leaf nitrogen content, specific leaf area (SLA), and net photosynthetic rate increased significantly by 199.9%, 45.7%, and 27.1%, respectively, indicating an efficient acquisitive strategy of “high-investment and high-return”. Under the high N treatment, leaf nitrogen content and SLA significantly increased relative to the control, whereas the net photosynthetic rate decreased significantly compared to the low N treatment, and photosynthetic nitrogen-use efficiency (PNUE) dropped by 76.8% compared with the control, indicating an inefficient acquisitive strategy of “investment-return imbalance”. These changes in leaf functional traits indicated that long-term N addition drove a shift in resource-use strategy of C. angustifolia from conservative to acquisitive. There was no difference in overall phenotypic plasticity between the low and high N treatments, but the response magnitudes of the 14 functional traits varied. Leaf nitrogen content and leaf N:P exhibited the strongest plasticity. The plasticity of net photosynthetic rate, stomatal conductance, transpiration rate, PNUE, and water use efficiency (WUE) was higher under the low N treatment. Phenotypic integration under high N treatment was significantly higher than under the low N treatment, with tighter correlations among leaf functional traits. Phenotypic plasticity and phenotypic integration showed no correlation, suggesting that they acted as relatively independent dimensions, playing roles in optimizing resource utilization and coping with environmental stress, respectively.

Soil erosion is severe in the red soil hilly region of southern China, where biocrusts widely develop on the surface of degraded and exposed soil, playing a critical role in regional eco-hydrological processes. From July to October 2024, we conducted an experiment with uncrusted degraded red soil and typical moss-crusted degraded red soil at the Ecological Experiment Station of Red Soil, Chinese Academy of Sciences, in Yujiang District, Yingtan City, Jiangxi Province. To elucidate the differences of soil water movement characteristics between biocrusts and uncrusted soil in degraded red soil regions, we investigated the infiltration processes and water flow types of uncrusted soil and biocrusts (moss crusts) through double-ring infiltration and in-situ dye-tracing experiments. The results showed that moss crusts significantly altered the physicochemical properties of the 0-10 cm depth of soil. Specifically, soil bulk density and saturated hydraulic conductivity of moss crusts was significantly reduced by 9.1% and 176.5%, while organic matter content, clay content, silt content, and surface roughness were 58.2%, 35.3%, 45.0%, and 201.7% higher than that of uncrusted soil, respectively. Compared to uncrusted soil, moss crusts greatly diminished soil infiltration, with initial infiltration rate, steady-state infiltration rate, average infiltration rate, and cumulative infiltration being reduced by 11.8%, 53.3%, 50.0%, and 50.9%, respectively. Moss crusts suppressed infiltration, resulting in a 29.7% reduction in the 0-10 cm stained area ratio and a 57.9% decrease in the stained path width <100 mm in comparison to uncrusted soil. Furthermore, the stained path number of moss crusts was 1.5 times of uncrusted soil. Moreover, the horizontal stained images also revealed that moss-crusted soil exhibited a higher number of water flow paths and a larger equivalent width compared to the uncrusted soil at 0-10 cm depth. The water flow pattern of moss crusts was predominantly exhibited heterogeneous finger flow (concentra-ted at 0-1 cm depth of soil) and highly interacted macropore flow, and without any homogeneous flow. Uncrusted soil exhibited predominantly homogeneous flow in the 0-3 cm depth, heterogeneous finger flow in the 3-8 cm, and highly interacted macropore flow below 8 cm. Results of Mantel test and structural equation modeling revealed that infiltration rate exhibited significant correlations with stained area ratio, surface type, and organic matter content. Especially, surface type (uncrusted soil and moss-crusted soil) exerted a direct and significant effect on soil infiltration and also indirectly influenced stained area ratio and soil infiltration by modifying other soil properties. In conclusion, moss crusts that developed on degraded and exposed red soil surfaces in subtropical regions could significantly alter the basic physicochemical properties and hydraulic parameters of surface soils. It markedly reduced the infiltration rate, suppress infiltration, and ultimately change soil water flow type. Thus, moss crusts play a cardinal role in surface ecological restoration in degraded red soil regions.

Elucidating the response of rhizosphere fungal communities to pruning intensity in Rubus corchorifolius is critical for refining branch-thinning practices and optimizing rhizosphere soil management. Taking 2-year-old branches of R. corchorifolius as research materials, we set three pruning intensities: no basal pruning (control), removal of 1/5 of primary lateral branches (light thinning), and removal of 1/3 of primary lateral branches (heavy thinning). We conducted pruning 15 days before the flowering period and collected rhizosphere soil at early flowering stage, early fruiting stage, and fruit ripening stage to analyze the changes in soil nutrient content and fungal community structure and function. The results showed that at early flowering and early fruiting, light thinning increased soil organic matter, organic carbon, total nitrogen, available nitrogen, and available potassium by 4.5%-44.1%, whereas heavy thinning decreased organic matter, organic carbon, total nitrogen, and available nitrogen by 2.5%-18.2%. At fruit ripening stage, all thinning treatments significantly elevated total phosphorus, organic matter, organic carbon, available nitrogen, available phosphorus, C/N, and C/P, with increases ranging from 9.2% to 136.8%. Thinning reduced fungal community diversity at early flowering and early fruiting, but increased richness at fruit ripening. Light thinning enriched Russula at early flowering and Mortierella and Archaeorhizomyces at early fruiting, while heavy thinning enriched Isaria at early flowering and Hydnum at fruit ripening. Redundancy analysis indicated that community composition under both thinning treatments was positively modulated by available potassium at early flowering and early fruiting stage, and by available nitrogen (light thinning) and available phosphorus (heavy thinning) at the ripening stage. Pruring increased the proportion of soil saprotrophs at fruit ripening stage and the mycorrhizal fungal fraction during early flowering and early fruiting stage. Overall, light thinning performed half a month before flowering could favor soil nutrient accumulation, improve fungal community structure, and increase the relative abundances of saprotrophs and mycorrhizal fungi, collectively exerting positive effects on soil nutrient cycling and growth of R. corchorifolius.

The “Grain for Green” program, a key measure for soil and water conservation and ecological restoration on the Loess Plateau, profoundly affects soil ecological processes. However, existing research mostly focuses on topsoil. How returning farmland to forest regulates bacterial communities in deep soil and the response mechanisms remain unclear. Taking Robinia pseudoacacia plantation (25 a) after returning farmland to forest and cropland with similar fallow periods in a typical arid area of the Loess Plateau as research subjects, with the topsoil layer (0-20 cm) as the reference, we analyzed bacterial diversity, community composition, and their relationship with soil physicochemical factors in deep soil layer (160-200 cm). The results showed that, in the topsoil, the total carbon content of R. pseudoacacia plantation was significantly 7.4% higher than that of cropland, while the available phosphorus content was 80.5% lower. In the deep soil, the total carbon content of R. pseudoacacia plantation was significantly 17.6% higher than that of cropland, and total phosphorus content and soil water content were significantly reduced by 15.6% and 63.5%, respectively. For the inter-layer comparison, total nitrogen content and water content in the deep soil of R. pseudoacacia plantation were significantly lower than those in the topsoil, while soil pH value increased significantly. For cropland, total carbon and total nitrogen contents in the deep soil were significantly lower than those in the topsoil, and pH value also increased significantly. Bacterial α diversity indexes (Chao1 index and phylogenetic diversity index) were significantly higher in topsoil than in deep soil. Moreover, the indices of α diversity in the both soil layers of the R. pseudoacacia plantation were significantly lower than those of cropland. The interaction between land use type and soil layer significantly affected bacterial community composition, together explaining 48.3% of the community variation. The abundance of oligotrophic bacterial groups such as Chloroflexi and Actinomycetes in the deep soil of R. pseudoacacia plantations increased by 19.7% and 65.0% respectively compared to cropland, while the abundance of copiotrophic bacterial groups such as Proteobacteria decreased by 26.9%. The response of bacterial community to environmental factors exhibited significant vertical differentiation. The topsoil community was regulated by nitrogen, phosphorus, and water availability, while the deep soil community was mainly driven by soil carbon storage and water content. Compared with croplands, R. pseudoacacia plantations had higher bacterial network complexity and stability, with significant differences between topsoil and deep soil. In summary, returning farmland to forest altered soil physical and chemical properties, and reshaped the composition and vertical distribution of soil bacterial communities, promoting a shift towards oligotrophic bacteria in deep soils, thereby affecting nutrient cycling, carbon sequestration, and water balance in deep soils.

How the mycorrhizal type of tree species regulates the composition and assembly processes of rhizosphere bacterial communities remains unclear. We selected five arbuscular mycorrhizal (AM) and five ectomycorrhizal (EcM) tree species from two typical forests across different climatic zones, namely a subtropical evergreen broadleaved forest at Tiantong Station in Zhejiang and a temperate broadleaved Korean pine forest at Maoershan Station in Heilongjiang. We analyzed the rhizosphere soil physicochemical properties and bacterial community composition, and quantified the assembly processes of bacterial communities by using niche breadth and null model analyses. The results showed that forest type was the dominant factor driving variation in rhizosphere soil bacterial communities (explaining rate 62.6%), with a small contribution from mycorrhizal type (2.6%). However, mycorrhizal effects differed significantly among forest types and bacterial abundance levels, including all species, abundant species, and rare species. Soil nitrogen availability, especially ammonium, was a key factor regulating the structure of rhizosphere bacterial communities. The standardized effect size (SES) values of rhizosphere bacterial communities in both forests were all greater than 2, indicating that deterministic processes dominated the assembly of these communities. The influence of mycorrhizal type on the assembly processes of rhizosphere bacterial communities exhibited significant forest-type dependence. At Tiantong Station, deterministic processes had a stronger influence on AM tree species, whereas at Maoershan Station, this influence was stronger for EcM tree species. This study revealed the dominant role of deterministic processes in the assembly of rhizosphere bacterial communities of mycorrhizal tree species, and this role was dually regulated by forest type and mycorrhizal type.

Enclosure is one of the key measures for restoring degraded grasslands. The enhancement of carbon sequestration after grassland restoration is directly related to the improvement of regional ecological quality and the achievement of carbon neutrality goals. We conducted an in-situ root growth experiment lasting for four years (6, 12, 24, and 48 months) using the internal growth core method across natural grassland and grasslands with different closure durations (5, 10, 25, and 30 years) in Yunwushan National Nature Reserve. We explored the duration effect on root growth and globulin-related soil protein (GRSP) carbon sequestration in enclosed grasslands. The results showed that in plots with different closure durations, root biomass in growth bags significantly increased with the duration of closure, reaching a peak (0.36 g per bag) in the 25-year closure plot, which was a 125.0% increase compared to that in the natural grassland. The GRSP content increased simultaneously with the root biomass, reaching a maximum value (3.16 g·kg^-1 ) in the 25-year closure plot. Partial least squares path model analysis revealed that root biomass and GRSP drove soil organic carbon sequestration by promoting the accumulation of particulate organic carbon (path coefficients of 0.18 and 0.33, respectively), which in turn affected soil organic carbon sequestration (path coefficient=0.47). Principal component (PC) analysis indicated that the PC1 score was highest in the 25-year closure plot, suggesting that the accumulation of reactive carbon pool reached its optimal level. At this stage, the soil organic carbon and mineral-bound organic carbon conten were also the highest, confirming that 25 years of closure is a key milestone for carbon pool accumulation. We recommended that grasslands in this region be moderately utilized after 25 years of closure to accelerate nutrient cycling and further enhance the carbon sink potential of the grasslands.

Evaluating the external value of rice production environment in the Yangtze River Economic Belt can make up for the lack of attention to the pre-production link of rice in literature, and thus provide a basis for promoting agricultural green production. Based on the panel data of rice production in the Yangtze River Economic Belt from 2000 to 2024, we used the functional value method and the equivalent factor method to calculate the 20 environmental externalities across 11 provinces and cities in the Yangtze River Economic Belt, and analyzed the spatial and temporal variations. The results showed that the annual environmental positive, negative externality and net value of rice production from 2000 to 2024 in the Yangtze River Economic Belt were 344.476 billion, 284.605 billion, and 59.871 billion yuan, respectively. The positive externality value was mainly composed of water conservation (50.1%) and gas regulation (21.7%). The negative externality value was mainly composed of water consumption (27.8%), fertilizer pollution (27.2%), and greenhouse gas emissions (22.2%). During the study period, the overall value of positive externality showed a downward trend, and the value of negative externality showed a trend of increasing first and then decreasing with 2012 as the demarcation point. The average annual net external value of rice production environment in the lower, middle, and upper reaches of the Yangtze River Economic Belt was 7.892 billion, 46.679 billion, and 6.099 billion yuan, respectively. The net external value of rice production in Jiangxi and Hunan was the highest, which together contributed more than 2/3 of the whole study area. The net external value of Yunnan was the lowest. Our results could provide scientific basis for the optimal layout and green transformation of rice production in the Yangtze River Economic Belt.

We examined the effects of different combined soil amendments on the quality of saline-alkali soil and on the growth, yield, and quality of watermelon in a field experiment. There were four treatments, including 75 kg·hm^-2 sulfur fertilizer+600 kg·hm^-2 bio-organic fertilizer (T₁), 75 kg·hm^-2 sulfur fertilizer+300 kg·hm^-2 soil conditioner (T₂), 600 kg·hm^-2 bio-organic fertilizer+300 kg·hm^-2 soil conditioner (T₃), and 75 kg·hm^-2 sulfur fertilizer+600 kg·hm^-2 bio-organic fertilizer+300 kg·hm^-2 soil conditioner (T₄), with no amendment application as the control (CK). We analyzed the effects of different treatments on soil pH, soil salt content in the 0-100 cm soil profile, as well as photosynthetic characteristics, growth, yield, and fruit quality of watermelon. The results showed that all amendment treatments reduced soil pH and salt content to different extents. The decrease in soil pH was mainly concentrated in the 0-60 cm soil layer. The treatments of T₃ and T₄ showed more obvious effects on reducing soil pH in the 20-40 cm soil layer. The T₂ treatment had a more prominent effect on reducing soil salt content, with a reduction of 13.8% and 29.5% in the 0-20 cm and 20-40 cm soil layers, respectively. The T₂ and T₃ treatments significantly increased net photosynthetic rate, transpiration rate and stomatal conductance of watermelon. The T₂ treatment mainly promoted leaf area expansion and main vine elongation. The T₃ treatment mainly promoted main vine elongation and stem thickening. The T₁, T₂, T₃, and T₄ treatments increased watermelon yield by 8.9%, 12.4%, 12.3%, and 11.0%, respectively. The T₃ treatment significantly increased fruit hardness, while the T₂ and T₄ treatments significantly increased soluble solids, vitamin C content, and sugar-acid ratio. Based on the multi-criteria decision-making model, the comprehensive ranking of different treatments on watermelon was T₂>T₃>T₄>T₁>CK. Overall, the combined application of 75 kg·hm^-2 sulfur fertilizer and 300 kg·hm^-2 soil conditioner was the optimal treatment for improving saline-alkali soil, promoting watermelon growth, increasing yield and improving fruit quality.

Michelia shiluensis is a rare tree species in the family Magnoliaceae endemic to southern China. Its natural distribution regions frequently affected by acid rain, exposing it to a high risk of acid rain stress. In this study, 3-year-old seedlings of M. shiluensis were subjected to simulated acid rain treatments at pH 2.5, 3.5, 4.5, and 5.0, with purified water (pH 7.0) as control, for a 50-day experiment. We investigated changes in plant growth, leaf anatomical structure, and photosynthetic physiological parameters. The results showed that acid rain stress significantly inhibited plant growth, and that the effect became more severe with decreasing pH. Under the pH 2.5 treatment, plant height and ground diameter decreased by 82.3% and 87.4%, respectively. All the treatments with pH≤4.5 significantly increased stomatal area, with that of individual stomata being increased by 47.6% and 76.6% under pH 3.5 and pH 2.5 treatments, respectively. Under pH≤3.5, the thickness of all leaf anatomical tissues increased significantly, and the mesophyll became more compact. During the stress period, net photosynthetic rate continuously declined, while the intercellular CO₂ concentration increased during the middle and late stages of stress. Under pH≤3.5, the maximum photochemical efficiency of PSⅡ remained relatively stable, whereas the photochemical quenching coefficient and electron transport rate increased transiently during the early stage of stress but gradually declined thereafter. In contrast, both parameters remained suppressed under the pH 2.5 treatment. In conclusion, acid rain reduced net photosynthetic rate and inhibited the growth of M. shiluensis by disrupting stomatal structure, increasing the resistance to CO₂ diffusion within the mesophyll, and suppressing the photochemical activity of photosystem Ⅱ. Photosynthetic activity was markedly inhibited at pH≤3.5, whereas severe damage to both leaf structure and photosynthetic capacity occurred under the pH 2.5 treatment.

To accurately simulate carbon fluxes of southern poplar plantations, we applied the PEST parameter optimization method to calibrate the ecophysiological parameters in the Biome-BGC model based on eddy covariance flux tower. We simulated the daily gross primary productivity (GPP) and ecosystem respiration (Re) of the plantation, and identified the sensitive parameters and main meteorological drivers. The results showed that the simulation accuracy of the model for GPP and Re was significantly improved after parameter optimization. The coefficients of determination (R²) for GPP and Re reached 0.74 and 0.63, respectively, which were 27.6% and 31.3% higher than those before optimization. The mean absolute error (MAE) for GPP and Re decreased by 15.6% and 7.5%, and the root mean square error (RMSE) for GPP and Re decreased by 16.9% and 5.9%, respectively. The average GPP and Re simulated by the model over five years were 1.71 and 1.55 kg C·m^-2·a^-1, respectively. Sensitivity analysis showed that leaf carbon-nitrogen ratio and the canopy light extinction coefficient strongly affected carbon flux simulation, and the fraction of leaf nitrogen in Rubisco and the litter carbon-nitrogen ratio were moderately sensitive parameters. Path analysis showed that air temperature and shortwave radiation flux density were the main meteorological factors driving the increase in GPP on the daily scale. Air temperature, precipitation and shortwave radiation flux density significantly promoted the increase in Re, with the effect of air temperature being the strongest. In summary, the PEST parameter calibration substantially improved Biome-BGC performance for carbon flux simulation in southern poplar plantations. The key sensitive parameters affecting the simulation accuracy were leaf carbon-nitrogen ratio and canopy light extinction coefficient. The key meteorological factor that dominated GPP and Re changes was air temperature.

To identify the major drivers of lightning-caused fire and to develop predictive models in the Greater Khingan Mountains, we integrated multi-source data from 2021 to 2024, including lightning records, forest fire records, and multi-source environmental data. We identified candidate lightning events using a spatiotemporal mat-ching approach, and addressed the imbalance problem of sample type using the EasyEnsemble method to construct the model dataset. We then selected predictor variables through correlation analysis, collinearity diagnosis, and feature importance analysis, developed multiple statistical and machine learning models, and interpreted the final model by SHAP (SHapley Additive exPlanations). The results showed that a total of 103 lightning events associated with lightning-caused fires were identified. The average distance between lightning strikes and fire ignition points was 0.84 km, with a mean holdover time of 1.4 days. 83.5% of fires were detected within three days after lightning occurrence. The predictive model identified the duff moisture code, drought code, and hourly fire weather index as the primary predictors, with temperature and wind speed as the secondary predictors. The random forest model showed the best overall performance, with an AUC of 0.7959, sensitivity of 0.7229, and specificity of 0.7752. The optimal classification thresholds were mainly concentrated between 0.45 and 0.55. The occurrence of lightning-caused fire was jointly influenced by fire weather, meteorological, topographic, and lightning-related factors, exhibiting significant nonlinear and threshold effects.

Quantifying the spatiotemporal patterns and driving mechanisms of ecosystem services in the agro-pastoral transition zone of northern China is crucial for maintaining their regional ecological barrier functions and achieving sustainable land management. Based on the InVEST, CASA, and RWEQ models, we evaluated five key ecosystem services (food production, carbon sequestration, soil and water conservation, windbreak and sand fixation, and water yield) from 2000 to 2020 in the agro-pastoral transition zone of northern China, and further combined spatial statistics and machine learning methods to reveal their spatiotemporal differentiation characteristics and dominant driving factors. The results showed strong spatial variations. High-value areas of food production were distributed in the eastern plains, while high-value areas of carbon sequestration and soil and water conservation were stably distributed in the southern region and along mountain ranges. High-value areas of windbreak and sand fixation were located in the north, and high-value areas of water yield were mainly situated in the south and west. From 2000 to 2020, ecosystem services displayed stage-specific evolutionary characteristics. Food production increased continuously, with the total volume growing from 2.32×10⁷ t to 6.53×10⁷ t. Carbon sequestration generally increased, rea-ching a peak of 10.7×10⁷ t in 2015 before slightly declining. Soil and water conservation fluctuated upward, reaching a high value of 3.63×10⁹ t in 2010, decreasing slightly in 2015, and then peaking at 4.03×10⁹ t in 2020. Water yield rose slowly and tended to stabilize after 2010. Windbreak and sand fixation changed most drastically, first decreasing from 4.28×10⁹ t in 2000 to 2.98×10⁹ t in 2010, and ultimately rising to 14.7×10⁹ t in 2020. The driving mechanisms for each ecosystem service were distinctly differentiated. Precipitation was the strongest positive driving factor for water yield (SHAP value was 67.95). Elevation dominated the spatial distribution pattern of food production (SHAP value was 64.47). Slope showed a strong negative association with soil and water conservation (SHAP value was 38.28). Wind speed was the primary limiting factor for windbreak and sand fixation (SHAP value was 7.02), and its changes were jointly driven by wind speed and the positive contribution of precipitation. Carbon sequestration showed negative associations with nitrogen deposition, wind speed, and precipitation. Ecosystem ser-vices in the agro-pastoral transition zone of northern China exhibited spatiotemporal heterogeneity, with synergetic and trade-off relationships coexisting among different services, reflecting multifunctional coupling. Based on the differences in driving mechanisms between natural conditions and human activities, regional ecological management should implement zoned and classified regulation to optimize the structure of ecosystem services.

The seasonal variation characteristics of vegetation gross primary productivity (GPP) and its response mechanisms to climatic and vegetation structural factors represent a key scientific issue for assessing regional carbon sink functions. Based on MODIS GPP, leaf area index (LAI), and meteorological data from 2003 to 2020, we comprehensively employed trend analysis, partial correlation analysis, and multiple linear regression to investigate the spatiotemporal variations of GPP in spring, summer, and autumn at the seasonal scale in the Qinling-Daba Mountains. We further explored the synergistic driving mechanisms of vegetation structure and climatic factors. The results showed that, from 2003 to 2020, GPP in spring, summer, and autumn all exhibited significant increasing trends, with the magnitude ranked as summer > spring > autumn, and the proportions of areas with significant increasing trends were 82.9%, 64.1%, and 20.6%, respectively. LAI increased significantly in all the three seasons, with the proportion of increasing areas exceeding 86.9%. In spring, precipitation showed an overall fluctuating upward trend, vapor pressure deficit (VPD) displayed a downward trend, while temperature remained relatively stable. In summer, both precipitation and VPD exhibited overall downward trends, while maximum temperature showed a significant upward trend, indicating a certain warming-drying trend in the climate. In autumn, precipita-tion increased slightly, while temperature and VPD remained relatively stable. Regarding the temporal effects of climatic factors, there were significant seasonal differences. In spring, precipitation was mainly characterized by lag effects, temperature by synchronous effects, and VPD by cumulative effects. In summer, all climatic factors were mainly characterized by synchronous effects. In autumn, precipitation, maximum temperature, and VPD were domi-nated by synchronous effects, while minimum temperature was mainly controlled by cumulative effects. LAI was the primary positive driving factor for the seasonal-scale increase in GPP. Temperature factors predominantly exerted promoting effects. Precipitation showed inhibiting effects in spring and autumn but promoting effects in summer. VPD exhibited inhibiting effects in both spring and summer, but a weak promoting effect in autumn. At the seasonal scale, we revealed the dominant driving mechanism of improved vegetation canopy structure on GPP enhancement in the Qinling-Daba Mountains, providing scientific basis for evaluating the carbon sink function of regional ecosystems.

Under the backdrop of rapid urbanization, the imbalance between supply and demand of ecosystem ser-vices has become a major issue affecting watershed ecological security and sustainable development. Exploring the spatial supply-demand pattern of ecological space and zoning-based management and control is of great significance for supporting efficient management of regional ecological risks. Taking the Dongting Lake basin as an example, we employed the InVEST model to quantify the single and comprehensive supply-demand patterns of four typical ecosystem services (soil conservation, carbon sequestration, habitat quality, and water yield) in 2020. We further used the bivariate local spatial autocorrelation model and coupling coordination model to explore the coupling between “supply-demand state-land use intensity”, and delineated ecological management zones. The results showed that the supply and demand of ecosystem services in the Dongting Lake basin exhibited significant spatial heterogeneity in 2020. Natural ecosystems such as forest, grassland, and water body had relatively high supply, and the spatial distribution of the supply-demand relationship was relatively uniform. Construction land and cropland had relatively high demand, with spatial heterogeneity of the supply-demand relationship. The average supply-demand ratio of ecosystem services was 0.06, dominated by the low supply-low demand and low supply-high demand types. The supply-demand ratios of ecosystem services varied significantly among different land use types, with that of construction land being -0.62, showing the most prominent supply deficit, while forest (0.43) and grassland (0.33) exhibiting obvious supply surplus. The coupling coordination degree between the supply-demand ratio of ecosystem services and land use intensity exhibited a spatial pattern of “high in the periphery and low in the central area”. Based on this, four ecological management zones were delineated, namely ecological supply-demand coordination zone, ecological enhancement guidance zone, ecological risk restoration zone, and urban development control zone. Our results would provide scientific reference for the ecological management of the Dongting Lake basin.

Investigating the characteristics and formation mechanisms of the spatial association network of ecological vulnerability in the Yellow River Basin is of great significance for identifying regional ecological risk transmission pathways and promoting coordinated governance. We constructed an evaluation index system for ecological vulnerability based on the sensitivity-resilience-pressure model, calculated the ecological vulnerability index for the Yellow River Basin from 2013 to 2024 using the entropy method, and employed social network analysis and exponential random graph models to explore the characteristics and influencing factors of the spatial association network of ecological vulnerability. The results showed that ecological vulnerability in the Yellow River Basin exhibited a spatial pattern of low in the west and high in the east. The average connectivity of the ecological vulnerability network was 1, with an average hierarchy of 0.01, indicating a highly connected and flat-structured network. The capi-tals of the related provinces and their surrounding cities demonstrated strong inward attraction and outward radiation within the network. Apart from node attributes such as economic development level and population density significantly facilitating network formation, endogenous structural variables like reciprocity were also significant, indicating that inter-city ecological vulnerability associations were influenced not only by exogenous factors but also by notable endogenous dependencies. Moreover, the network was significantly affected by geographical adjacency and administrative subordination relationships. These findings provide empirical support for formulating regional ecological governance strategies from a network collaboration perspective.

Spatiotemporal dynamics of atmospheric CO₂ concentrations are crucial to understanding global carbon cycle and predicting regional climate change. Given that China spans multiple climatic zones and features complex and diverse ecosystems, elucidating the patterns of CO₂ differentiation across climatic zones are essential for formulating refined and differentiated reduction strategies. Here, we investigated the spatiotemporal variations of atmospheric CO₂ concentrations in China by using the satellite-retrieved XCO₂ datasets from 2003 to 2023 and the Köppen-Geiger climate classification. The results showed that the average of CO₂ concentrations ranked as: tempe-rate zone>tropical zone>cold zone≈arid zone>polar zone, while its growth rate ranked as: tropical zone>temperate zone>polar zone>cold zone≈arid zone. CO₂ concentrations had increased synchronously across climatic zones, yet the interregional CO₂ concentration differences had further widened, revealing an intensifying trend of spatial differentiation. Nearly half of the regions exhibited significant spatial clustering of atmospheric CO₂ concentration. The high-high clusters were primarily concentrated in the temperate zone, which was densely populated and economically developed. The low-low clusters were mainly distributed in the cold and polar zones, where ecological conservation was relatively robust. The spatial clustering was weakest in 2006 (Moran’s I=0.68, Z=70.00) and peaked in 2017 (Moran’s I=0.88, Z=90.33). While downward shortwave radiation was negatively correlated with CO₂ concentration (r=-0.542), population density (r=0.992), carbon emissions (r=0.970), leaf area index (r=0.845), temperature (r=0.565), and precipitation (r=0.481) all exhibited significant positive correlations with CO₂ concentration. Soil water content (r=0.072) showed a non-significant positive correlation with CO₂ concentration. According to the optimal parameters-based geographical detector, population density exerted the strongest influence on the spatial pattern of CO₂ concentration (q=0.55), followed by temperature (q=0.43). The interaction types between factors were predominantly characterized by bi-linear or nonlinear enhancement.

As an important component of the atmosphere, aerosols significantly influence regional climate and environment through scattering and absorption of solar radiation. To reveal the spatiotemporal evolution patterns of aerosol optical properties in Liaoning Province, we analyzed the spatiotemporal distribution characteristics and evolution trends of aerosol optical depth (AOD) in Liaoning Province based on the reanalysis data of AOD from 1994 to 2023. The results showed that the annual average AOD from 1994 to 2023 in Liaoning Province exhibited a distribution pattern of higher values in the south and lower values in the north, with the southern and coastal areas being the high-value centers (average value 0.43), while that in the west and north were the lowest (0.30). From 1994 to 2012, the annual average AOD in Liaoning Province increased by 0.007, and it decreased by 0.011 from 2013 to 2023, confirming the critical role of national emission reduction policies in the long-term reduction of aerosols in the northeastern region. Due to the combined effects of spring dust weather, high-temperature and high-humidity conditions in summer, and the increase in aerosol hygroscopicity and boundary layer uplift the monthly scale AOD in Liaoning Province, which showed a single-peak distribution. From January to February, the AOD was at the lowest level of the year (0.20), reaching its peak in June (0.58), and returning to the low value area in winter from November to December. The summer aerosol load was about 2.9 times that of winter. The results could provide data support for consolidating the achievements of air quality improvement.

Against the backdrop of built stock renewal and low-carbon transition, we constructed a evaluation framework from the dimensions of “adequate spatial conditions but insufficient practical actions” and “strong willingness with poor implementation feasibility”, which covered built environment and behavioral intention to address the dilemmas in community renewal. Taking 35 communities in the central urban area of Nanjing as objects, a total of 766 valid questionnaire responses were collected. We used the entropy weight-TOPSIS method, the Fogg behavior model, and GIS spatial analysis to quantitatively assess and classify the low-carbon renewal potential of target communities. The results revealed a widespread mismatch between community built environment and low-carbon intention of residents. The low-carbon renewal potential of the community was categorized into four types based on their matching degrees, with significant spatial distribution differences. The collaborative leading type (accounting for 6%) was concentrated in the central downtown and riverside zones. The environment-leading type (37%) was clustered in the central main urban area. The intention-leading type (46%) was mostly located in the peripheral downtown and riverside new towns. The dual-low constrained type (11%) was scattered across outer riverside areas. Targeted differentiated collaborative renewal strategies were proposed accordingly. As a leading demonstration zone, collaborative leading communities should promote deep energy-saving transformation and joint construction and governance. Environment-leading communities should focus on scene micro-scale updates to enhance convenience, stimulate action motivation, and trigger mechanisms. Intention-leading communities should address the shortcomings of facilities and promoting basic renovation for those who are willing to take the lead, combined with participatory discussions to lower the threshold for implementation. Dual-low constrained communities should adopt gradual updates, prioritize improving basic livability and energy-saving conditions, and cultivate low-carbon capabilities. This study could provide scientific decision support for the high-quality green and low-carbon renewal of urban communities across China.

Microtus fortis prefers to feed on the leaves of Broussonetia papyrifera, which would inhibit its reproduction. We focused on the key gene BpMYB56 in B. papyrifera that responds to rodent feeding, constructed BpMYB56 overexpressing B. papyrifera (OE1-OE3), and compared their nutritional differences with wild-type B. papyrifera (WT). We evaluated the attractiveness of overexpressing B. papyrifera leaves to the M. fortis and their effects on body weight and organs when mixed with typical rodent sterilants, such as α-chlorohydrin, curcumol, and tripto-lide, at a ratio of 50:1. The results showed that the contents of crude protein, crude fat, crude fiber, crude ash, soluble sugar, Ca, Fe, P, and total flavonoids in the leaves of overexpressing B. papyrifera were all higher than those in WT. Among the lines, OE3 exhibited the highest content for each component, being 1.2, 1.1, 1.3, 1.1, 1.6, 1.2, 1.1, 1.4, and 1.2 times those of WT, respectively. Except for crude ash, all differences reached a signifi-cant level. The feeding trial results showed that under free-choice conditions, the attraction time of fresh OE3 leaves to female and male M. fortis were 1.9 and 1.8 times those of WT, and the single-attraction time were 1.4 and 1.7 times those of WT, respectively. However, for dried OE3 leaves, there were no significant differences in attraction time, attraction frequency, or single-attraction time compared with dried WT. Among the combinations of OE3 leaves with sterilants, the curcumol+OE3 group exhibited the best attractant effect, which was 3.1 times that of the WT group. None of the different combinations had a significant effect on body weight of M. fortis. Both the testicular index and testicular volume of male M. fortis only in the triptolide+OE3 combination were significantly lower than those in the WT group. Overexpression of BpMYB56 influenced the accumulation of nutrients and flavonoids in B. papyrifera leaves, thereby altering their attractiveness to M. fortis, particularly for fresh leaves. However, the attractiveness of the overexpression lines when combined with different types of rodent contraceptives varied, showing drug- and sex-specific effects.

To elucidate the effects of fire on soil nematode community structure and energy flow within the soil micro-food web across different forest types in the subtropical-temperate transition zone, we investigated soil nematode communities in broadleaf forest, mixed coniferous-broadleaf forest, and coniferous forest in the Xianshan forest area near Henan Dabie Mountains National Forest Ecosystem Field Observation and Research Station. We analyzed soil nematode community structure and micro-food web energy flow between burned and unburned plots, and explored the key driving factors. The results showed that fire significantly reduced the average total soil nematode abundance and the relative abundance of omnivore-predator nematodes across the three forest types by 30.3% and 58.9%, respectively. Meanwhile, fire significantly decreased the soil nematode maturity index and channel index by 10.9% and 22.6%, respectively. There were no significant changes in the relative abundance of microbe-feeding nematodes, plant-parasitic nematodes, or diversity indices. For broadleaf forests, fire significantly increased the Shannon diversity index, richness index, and enrichment index of soil nematodes by 9.5%, 26.9%, and 44.5%, whereas the maturity index and channel index decreased by 19.5% and 41.3%, respectively. Post-fire soil organic matter decomposition was predominantly mediated by the bacterial channel, and no changes were found in total nematode abundance or the relative abundance of any trophic group. In mixed coniferous-broadleaf forests, fire significantly reduced the relative abundance of omnivore-predator nematodes by 61.9%, but did not affect the relative abundance of microbe-feeding nematodes, plant-parasitic nematodes, or ecological indices. For coniferous forests, fire did not alter total nematode abundance, the relative abundance of any trophic group, or ecological indices. Nematode faunal analysis showed that fire increased the functional metabolic footprint of soil nematodes in broadleaf forests, but reduced that in mixed coniferous-broadleaf and coniferous forests. Fire resulted in more uniform energy flow distribution among different energy channels in the micro-food web of mixed coniferous-broadleaf forests. In contrast, energy flow through organic matter decomposition channels and predation channels in the micro-food web was inhi-bited in broadleaf and coniferous forests, with energy concentrated in the plant-parasitic channel and energy flow uniformity decreasing. Litter quality, soil available nitrogen content, and soil water content were the key environmental factors affecting soil nematode community composition. In conclusion, soil nematode communities in different forest types exhibited divergent responses to fire. Broadleaf forests showed stronger potential for biodiversity recovery and nutrient enrichment, mixed forests had improved energy flow uniformity in the micro-food web, and coniferous forests exhibited characteristics of functional inhibition and reduced metabolic activity. These results provide a scientific basis for regional ecological restoration and soil health assessment of burned forests in the subtropical-temperate transition zone.

Decapterus maruadsi is an important small pelagic fish species in the South China Sea. Effective assessment of stock status and formulation of management recommendations based on the best available science are urgently needed for the conservation and sustainable development of this species. Based on the Bayesian state space modeling framework, we assessed the stocks of D. maruadsi by integrating a surplus production function with fishery production data to establish a baseline assessment scenario. The results showed that the evaluation scheme constructed based on the Fox surplus production function and fishing vessel power exhibited the best fitting effect. The results derived from this scheme indicated that the fishing intensity of D. maruadsi population in the South China Sea initially increased and then decreased from 1990 to 2023, yet it remained at a relatively high level. Overall, the biomass showed a fluctuating downward trend. During the model evaluation period, the maximum sustainable yield (MSY) of D. maruadsi was estimated to be 497000 t. The biomass required to maintain MSY and fishing intensity required to maintain MSY were 644000 t and 0.79, respectively. In 2023, the biomass of D. maruadsi population in the South China Sea was 688100 t, which was greater than that required to maintain MSY. The fishing intensity was 0.52, which was lower than that required to maintain MSY. It was determined that D. maruadsi population in the South China Sea did not experience overfishing in 2023 and was at a healthy state. The prediction results showed that fishing at a limit of 120% of the 2023 catch (i.e., 427000 t) would result in an upward trend in biomass over the next decade. The sensitivity analysis results indicated that increasing the prior mean values of the population parameter initial resource consumption rate (P₁₉₉₀) and environmental carrying capacity would lead to an overestimation of biomass and an underestimation of fishing intensity, with P₁₉₉₀ having a more significant impact. In summary, the residual yield model based on Bayesian state space was suitable for the assessment of fishery resources of D. maruadsi in the South China Sea under limited data conditions. It was recommended to set the total allowable catch of D. maruadsi in the South China Sea at 427000 t, conduct continuous monitoring, and regularly update assessment results to improve resource conservation and management effectiveness.

Against the backdrop of arid and semi-arid climates, plantation degradation in the Three-North region of China has emerged as a critical constraint on regional ecosystem stability and the sustained provision of ecosystem services. We synthesized the major manifestations and plantation degradation in the Three-North region. Plantation degradation is commonly characterized by tree physiological dysfunction, accompanied by growth decline at indivi-dual and stand scales, stand structural instability, and a decline in ecosystem functions. From an integrated ecological and tree physiological perspective, we highlighted how key ecological drivers, including water stress, nutrient limitation, and tree species-site mismatch under drought stress, could induce hydraulic failure, carbon starvation, and imbalance in water-carbon coupling, thereby driving the transition of plantations from physiological decline to structural and functional degradation. Moreover, we emphasized that tree species with different water-use strategies exhibited distinct degradation pathways and risk profiles under drought stress, which were jointly regulated by hydraulic safety margins and carbon balance constraints. Despite growing attention, substantial gaps remained in identifying dominant driving factors, quantifying key physiological thresholds, and elucidating cross-scale coupling processes. Future studies should integrate multi-scale indicators, such as water use efficiency, to develop species- and region-specific diagnostic and early-warning frameworks for plantation degradation.

The cooling and dust retention functions of urban parks are hot topics in the research area of ecosystem services in urban parks. Although the response curves of both functions to park distance are highly coupled and regulated by similar environmental factors, those two functions are often studied separately. Given the lack of high-precision environmental monitoring methods, the following two scientific problems have not been solved. First, whether the dust retention effect of urban parks changes synergistically with the cooling gradient? Second, is there a spatial feedback mechanism among various ecological functions of urban parks? Overall, there is a significant knowledge gap in the field of urban green space research regarding the mechanisms of heat-pollution coupling. In this paper, we sorted out the concepts and influencing factors of cooling and pollution retention effects in urban parks, summarized the available methods and approaches for quantitative research from the dual perspectives of cooling and pollution retention, and synthesized the research progress of coordinated regulation of cooling and dust retention services in urban parks. We suggested to break through the traditional single-factor analysis paradigm, encourage the establishment of multi-functional coupling analysis model of urban green space cooling and dust retention, and systematically explain the spatio-temporal differentiation law of their joint action. It would provide spatial decision support and core scientific basis for exploring the optimization path of park spatial pattern guided by thermal pollution collaborative governance and achieving the paradigm shift of ecological service efficiency from “passive response” to “active regulation”.

Plant invasion poses a serious threat to biodiversity and ecosystem functions, while habitat heterogeneity significantly affects the invasion trend along latitudinal gradients. We reviewed the research progress on plant invasion and its biological interaction patterns along latitudes over the past decade. The phenotypic plasticity and ecolo-gical adaptability of many invasive plants increase with increasing latitude, thereby exacerbating the homogenization of native plant communities in high-latitude regions. The occurrence of natural enemy insects, insect feeding rates, soil pathogenic fungal infection rates, and feedback effects with soil biota of invasive/native plants exhibit asymme-tric patterns along latitudinal gradients. Climate warming has altered the multi-trophic interactions in invaded habitats, intensifying the “natural enemy release effect” of invasive plants and the “non-target effect” of invasion control in high-latitude regions. Future research should focus on exploring the redistribution of different functional secondary metabolites within invasive plants along latitudinal gradients; elucidating the latitudinal patterns and synergistic effects of “aboveground-belowground” interactions in invaded ecosystems based on multi-factor and multi-trophic interaction networks; investigating the functional trait evolution of invasive plants across latitudes and the phylogenetic relationships of co-existing plants in invaded areas; and comprehensively utilizing emerging technologies to reveal the molecular basis, co-evolution mechanisms, and latitudinal differentiation patterns of biological interactions in invasive plants. This study would deepen the understanding of plant invasion mechanisms and the prevention and control of biological invasions under global change.

Small watersheds are the fundamental units for ecological governance and agricultural development in mountainous regions, possessing an intact ecosystem structure and independent eco-economic functions. Integrating circular agriculture with soil and water erosion control at the small watershed scale can realize the coordinated advancement of ecological and economic benefits. Constrained by complex terrain and fragile ecological conditions, the circular agricultural systems in small watersheds of southern China mountainous areas are plagued by multiple bottlenecks, including incomplete planting-breeding circulation chains, insufficient quantitative evaluation of ecological effects, poor adaptability of core technologies, insufficient coordination of policies and mechanisms, and a shortage of interdisciplinary research. These constraints hinder the systematic integration and large-scale popularization of such systems. Based on circular economy theories and sustainable development goals, we analyzed the deve-lopment status of circular agricultural systems in small watersheds of southern China mountainous areas, covering four major dimensions: the integration of comprehensive soil and water erosion control with ecological agriculture, the combination of planting-breeding production and agricultural waste resource utilization, the construction of agroforestry compound systems, and the integrated development of characteristic industries and eco-tourism. We further analyzed the prevailing challenges, such as fragile eco-environments, imperfect technical and model standards, restrictions from capital investment and market mechanisms, as well as insufficient administrative coordination and professional talents. We then proposed corresponding optimization countermeasures from four dimensions: technological innovation, ecological conservation and restoration, industrial integration, and policy support plus organizational model innovation. This would provide a theoretical basis and practical references for constructing circular agricultural systems tailored to the characteristics of southern China mountainous areas and achieving harmonious development between agricultural exploitation and ecological protection.